Ye Shiwen reiterated her success was a result of hard work and dedication"

Chinese teenager Ye Shiwen might be setting the pool alight with some remarkable performances, but that has led to one of the most respected coaches in swimming to question the 16-year-old's sudden emergence.

The executive director of world swimming, John Leonard, called the female swimmer's performance "unbelievable, disturbing and suspicious", while saying it brought back memories of Irish swimmer Michelle Smith's race in Atlanta 1996 and old East German swimmers. Smith, now Michelle de Bruin, was handed a four-year ban after testing positive for an anabolic steroid in 1998.

Ye put in a stunning performance in the 400 meter individual medley on Saturday, setting a world record time. Her final 100 meters in freestyle, in 58.6 seconds, particularly caught the eye; in the final 50 meters, she was even faster than the split time of American Ryan Lochte, the winner of the corresponding men's event.

"We want to be very careful about calling it doping," Leonard, who is also the executive director of the USA Swimming Coaches Association, is quoted as saying by the Guardian.

"The one thing I will say is that history in our sport will tell you that every time we see something, and I will put quotation marks around this, 'unbelievable', history shows us that it turns out later on there was doping involved.

"That last 100 meters was reminiscent of some old East German swimmers, for people who have been around a while. It was reminiscent of the 400 meters individual medley by a young Irish woman in Atlanta.

"Any time someone has looked like superwoman in the history of our sport they have later been found guilty of doping."

Australian Stephanie Rice, who won gold in the 400 meter medley in Beijing, described the swim as "insanely fast" while Ariana Kukors, the 2009 world champion, said it was "amazing" and "unbelievable."

Leonard said all the coaches he had talked to, said the swim was "unbelievable."

"I have been around swimming for four-and-a-half decades now," he said. "If you have been around swimming you know when something has been done that just isn't right. I have heard commentators saying 'well she is 16, and at that age amazing things happen'. Well yes, but not that amazing. I am sorry.

"I use that word (unbelievable) in its precise meaning. At this point it is not believable to many people.

"No coach that I spoke to yesterday could ever recall seeing anything remotely like that in a world level competition.

"Where someone could out-split one of the fastest male swimmers in the world, and beat the woman ahead of her by three-and-a-half body lengths. All those things, I think, legitimately call that swim into question."

Asked about the questions being raised about her performance, Ye said: "The Chinese team keep very firmly to the anti-doping policies, so there is absolutely no problem."